Verb, transitive. Talk to someone in a friendly, informal way; schmooze. Most often used to suggest or imply flattery, as in “butter up,” and especially an attempt to flirt with or seduce the chattee. “At a Union 76 in Ontario, near Riverside, he saw a guy changing a headlamp, chatted him up, and learned that he was independent.” (John McPhee, The New Yorker, February 17, 2003)/”There’s a great scene toward the end of the film [“Diner”] when Boogie (Mickey Rourke) and Fenwick (Kevin Bacon) — two kids from downtown Baltimore — are driving through Maryland’s horse country and happen upon a comely young woman on horseback. The guys pull over and chat her up, and she says her name is “Chisolm, as in the Chisolm Trail,” and then gallops away.” (New York Times, January 26, 2011). Google Ngram.